The objective of this project is the discovery of new types of drugs which are clinically useful against cancer. The following topics are of current interest: (1) pyrimidine nucleosides as antitumor agents and transition-state enzyme inhibitors, especially inhibitors of cytidine deaminase and cytidine triphosphate synthetase, (2) pyridone nucleosides as antitumor agents, (3) diazepinone nucleosides as antitumor agents, (4) dinucleotide analogs structurally related to NAD as inhibitory agents of inosine monophosphate dehydrogenase, (5) N-chloroethyl derivatives of 2- and 4-pyridones as antitumor agents, and (6) antimelanoma agents based on catechols.